1. Technical Field
This invention relates to gas-cooled printed circuit boards incorporating an enhanced heat transfer structure, and more particularly to such circuit boards wherein the enhanced heat transfer structure includes flocked carbon fibers.
2. Background Art
Electronic modules containing printed circuit boards are often cooled, at least in part, by blowing a gas such as air, over the boards. Cooling is required because heat is typically generated by electronic components on the printed circuit boards. When the gas flows around these electronic components, heat is transferred to the gas by convection. Thereafter, the heated gas is exhausted from the module. However, these types of gas-cooled electronic systems often exhibit operational power limits dictated by the rate at which heat can be dissipated from temperature critical components on the circuit boards. These power limitations can result in lower system performance. Therefore, if the rate of heat transfer could be increased, the operational power might be increased, and system performance improved.
Attempts at enhancing the heat transfer in gas-cooled electronic systems have been made in the past. For the most part, heat transfer rates have been increased by increasing the effective heat transfer surface area of the temperature sensitive electronic components. Thus, more heat can be transferred to the gas per unit of time. One way of increasing this surface area has been to attach "pin fins" to the top of the temperature sensitive components. As shown in FIG. 1, a pin fin 12 is a structure having a base 14 which supports rows of upright pins 16. Pin fins 12 are made of a thermally conductive material which draws heat away from an underlying temperature sensitive component. This heat is then transferred to the gas flowing around the base 14 and pins 16 of the pin fin 12. The effective heat transfer surface area of the pin fin 12 is much larger than that of the electronic component to which it is attached due to the added surface area afforded by the pins 16. However, the increase in heat transfer is limited to the number and size of pins 16 that can be formed on the base 14 of the pin fin 12. Current methods for producing state-of-the-art pin fins can not optimize the number and size of the pins to maximize heat transfer rates. In addition, they can be expensive.
Therefore, what is needed is a way of inexpensively increasing the effective heat transfer surface area of temperature sensitive electronic components over that available from current state-of-the-art pin fins.